CVE-2026-62815: Microsoft QUIC Remote Code Execution Vulnerability

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-11 · updated 2026-10-30
Weakness: CWE-416

Description

Use after free in Microsoft QUIC allows an unauthorized attacker to execute code over a network.

Affected products

Microsoft Windows 11: before 10.0.22631.7517 — fixed in 10.0.22631.7517
Microsoft Windows 11: before 10.0.26100.9106 — fixed in 10.0.26100.9106
Microsoft Windows 11 25H2: before 10.0.26200.9106 — fixed in 10.0.26200.9106
Microsoft Windows 11 version 26H1: before 10.0.28000.2704 — fixed in 10.0.28000.2704
Microsoft Windows Server 2022: before 10.0.20348.5440 — fixed in 10.0.20348.5440
Microsoft Windows Server 2025: before 10.0.26100.33222 — fixed in 10.0.26100.33222
Microsoft Windows 11: from 10.0.22631.0 before 10.0.22631.7517 — fixed in 10.0.22631.7517
Microsoft Windows 11: from 10.0.26100.0 before 10.0.26100.9168 — fixed in 10.0.26100.9168
Microsoft Windows 11 25H2: from 10.0.26200.0 before 10.0.26200.9168 — fixed in 10.0.26200.9168
Microsoft Windows 11 version 26H1: from 10.0.28000.0 before 10.0.28000.2704 — fixed in 10.0.28000.2704
Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.5499 — fixed in 10.0.20348.5499
Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.33296 — fixed in 10.0.26100.33296

How to fix

Upgrade to a fixed version: Microsoft Windows 11 10.0.22631.7517; Microsoft Windows 11 10.0.26100.9106; Microsoft Windows 11 25H2 10.0.26200.9106; Microsoft Windows 11 version 26H1 10.0.28000.2704; Microsoft Windows Server 2022 10.0.20348.5440; Microsoft Windows Server 2025 10.0.26100.33222; Microsoft Windows 11 10.0.22631.7517; Microsoft Windows 11 10.0.26100.9168; Microsoft Windows 11 25H2 10.0.26200.9168; Microsoft Windows 11 version 26H1 10.0.28000.2704; Microsoft Windows Server 2022 10.0.20348.5499; Microsoft Windows Server 2025 10.0.26100.33296. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62815

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